This invention is generally directed to toner compositions, and more specifically to single component toner compositions containing therein magnetite particles and crosslinked resin components. In accordance with one embodiment of the present invention, there are provided toner compositions comprised of crosslinked resin particles, low molecular weight waxy materials including polyethylene and polypropylenes, magnetites, first and second additive particles, and certain optional charge enhancing additives. The aforementioned toner compositions are particularly useful for affecting the development of images in electrostatographic imaging systems wherein the utilization of carrier particles are avoided.
Single component toner compositions are known, reference for example U.S. Pat. No. 4,311,779, which discloses a magnetic developer with from about 45 to about 65 percent by weight of a magnetic material, and wherein there is selected a binder including specific copolymers of conjugated diolefins such as styrene butadiene. It is indicated in column 4, beginning at line 60, of this patent that it is necessary that the amount of finely divided magnetic material to be incorporated into the developer should be 45 to 65 percent by weight, and particularly 50 to 60 percent by weight. A similar teaching is present in related U.S. Pat. No. 4,315,064 directed to a copying method wherein the toner as illustrated in the U.S. Pat. No. 4,311,779 is utilized. In addition, disclosed in U.S. Pat. No. 4,495,267 is a magnetic toner with improved humidity dependency containing magnetite in a binder, and wherein the water soluble component content of the magnetite is lower that about 0.15 percent by weight, and the water content of the magnetite at a temperature of 20.degree. C., and a relative humidity of 60 percent, is lower that 0.3 percent by weight. Furthermore, illustrated in U.S. Pat. No. 4,495,268 is a photocopying process wherein a magnetic developer is selected with specific linear polymers which are not believed to be crosslinked and wherein there is selected a special form of isometric magnetite. Also of interest is U.S. Pat. No. 4,499,168 which is directed to developer powders comprising one or more vinyl type copolymers exhibiting peak value molecular weights, and an ethylene type olefin homopolymer or copolymer. Moreover, in U.S. Pat. No. 4,229,900 the disclosure of which is totally incorporated herein by reference, there is illustrated a process for developing images by electrically transferring a magnetic developer to an image bearing member in the presence of a magnetic field, and wherein the magnetic developer is insulating and contains from 10 to 50 percent by weight of magnetic toner particles which are from about 20 to 25 microns in size.
Described in U.S. Pat. No. 4,556,624 are electrostatic toner compositions comprised of a polyblend mixture of a crosslinked copolymer composition, and a second polymer, pigment particles, a wax component of a molecular weight of from about 500 to about 20,000, and a charge enhancing additive. As first resin particles, there may be selected crosslinked copolymer resins including styrene alkyl methacrylate crosslinked with, for example, divinyl benzene. The disclosure of the aforementioned patent is totally incorporated herein by reference.
In addition, there is illustrated in U.S. Pat. No. 4,433,040, the disclosure of which is totally incorporated herein by reference, electrophotographic toners containing a metal complex dye including dyes similar to those selected for the present invention as optional components with the primary exception that the dyes of the present invention contain thereon an NH.sub.4 +moiety, rather than an H+moiety as recited in the claims of the U.S. Pat. No. 4,433,040, although such a moiety is disclosed therein. Examples of resins that may be selected are outlined in column 2, beginning at line 64, none of which appear to encompass crosslinked resins; and further there is no indication in this patent with respect to, for example, the selection of first and second additive components selected for the developer compositions of the present invention. Furthermore, in U.S. Pat. No. 4,562,136 there is illustrated a two component dry type developer with the optional charge enhancing additives that may be selected for the developer compositions of the present invention wherein, for example, the anion A is NH.sub.4 +. This patent describes a two component developer with carrier particles coated with a silicone resin and toner particles containing the monoazo metal complex dye of the formula as illustrated, for example, in claim 1. The disclosure of the aforementioned patent, particularly with respect to the charge enhancing additive, is totally incorporated herein by reference.
Other patents of background interest include U.S. Pat. Nos. 4,563,409; 4,590,141; 4,401,741; 4,404,269; 4,388,396; and 4,576,888. In U.S. Pat. No. 4,563,409 there is disclosed a symmetric 2:1 metal complex of the formula as recited in claim 1, and an electrophotographic toner containing from 1 to 50 percent by weight of the aforementioned metal complex; and from about 50 to 99 percent by weight of a resin, reference claim 3, for example; U.S. Pat. No. 4,590,141 is directed to carrier particles for use in two component dry developers comprising a core material and a silicone resin layer coated on the surface of said core material and as an agent against abrasion of the carrier particles inorganic fortifying filler particles selected from the group consisting of silicon carbide and potassium titanate; U.S. Pat. No. 4,401,741 is directed to a magnetic one component type developer comprising an electrically insulating binder medium and a magnetic material powder with a positive or negative charge control agent dispersed in the binder medium, and a charge control agent having a polarity opposite to that of said charge control agent at a weight ratio of from 1/0.05 to 1/1.5; U.S. Pat. No. 4,404,269 is directed to a two component composite developer which comprises a mixture of magnetic toner particles and nonmagnetic toner particles, the improvement wherein the magnetic toner particles are comprised of certain components in specific ratios, and nonmagnetic toner particles comprising specific components inclusive of a negative charge control agent; U.S. Pat. No. 4,388,396 is directed to a process for developing electrostatic images wherein there is included in the developer an offset preventing agent selected from the group consisting of aliphatic fluorocarbon compounds and fluorochlorocarbon compounds; and U.S. Pat. No. 4,576,888 is directed to a toner comprising azoic pigment having a silica core as a coloring component and a coating of a mono or polyazoic dye chemically bonded to the surface of the silica core through an aminosilane coupling agent.
Although the aforementioned toner compositions are suitable for their intended purposes, there continues to be a need for new specific toner compositions, particularly single component compositions useful in electrostatographic imaging systems. More specifically, there is a need for toner compositions that are particularly useful in jumping development imaging processes as disclosed in the aforementioned U.S. Pat. No. 4,229,900. Also, there is a need for single component toner compositions which when incorporated into electrostatic imaging processes enable images of excellent resolution for extended time periods. Moreover, there is a need for single component toner compositions with crosslinked resin particles wherein the developed images are effectively transferred to suitable supporting substrates. There is also a need for single component toners which retain their homogeneous characteristics during the melt mixing process. In addition, there is a need for single component toners wherein pigments such as carbon black are not present. Furthermore, there is a need for single component toner compositios which, when incorporated into electrostatographic imaging and printing apparatuses there can be obtained images with high solid area density (1.1 density units or higher), high density line copy, uniform halftones with acceptable toner reproduction curves, clean background areas, and suitable transfer characteristics.